28 July 2021

an interesting start of a CIS-75 transmission

Interesting CIS-75 75Bd/250 FSK heard on 6404.0 KHz (cf): the encrypted data are preceeded by a sync sequence of reversals that - according to my measurements - is sent at the speed of 100Bd. My friend cryptomaster suggested that the 100Bd are actually the 50Hz taken from the AC mains. Given the instability, can be assumed that the equipment is operated "in the field" and is associated with the instability of the autonomous power supply.

Fig. 1

 TDoA runs indicate the Kaliningrad Oblast (
Kaliningradskaja oblast) as possible location of the Tx (figure 2).

Fig. 2


No comments:

Post a Comment